U.S. patent number 4,142,615 [Application Number 05/657,983] was granted by the patent office on 1979-03-06 for wheel drive assembly.
This patent grant is currently assigned to Caterpillar Tractor Co.. Invention is credited to Aleksander Mankowski, Peter Sidles, Jr..
United States Patent |
4,142,615 |
Sidles, Jr. , et
al. |
March 6, 1979 |
Wheel drive assembly
Abstract
A wheel driven by a planetary reduction gear train has a disc
brake pack acting between a fixed member and a rotating member for
stopping or slowing the rotation of the wheel. The disc brake pack
is mounted between the fixed and rotatable members before the
planetary reduction gear set is assembled on the shaft making it
possible to service the disc brake pack without removing the wheel
from the shaft. In one embodiment, the sun and planet gears act as
a pump for circulating cooling fluid to the disc brake pack.
Inventors: |
Sidles, Jr.; Peter (Oswego,
IL), Mankowski; Aleksander (Downers Grove, IL) |
Assignee: |
Caterpillar Tractor Co.
(Peoria, IL)
|
Family
ID: |
24639424 |
Appl.
No.: |
05/657,983 |
Filed: |
February 13, 1976 |
Current U.S.
Class: |
192/221.1;
74/391; 180/370; 180/372; 188/71.5; 188/71.6 |
Current CPC
Class: |
B60K
17/046 (20130101); B60T 1/062 (20130101); F16D
55/40 (20130101); F16H 1/28 (20130101); F16D
65/853 (20130101); Y10T 74/19545 (20150115); F16D
2055/0058 (20130101) |
Current International
Class: |
F16D
65/853 (20060101); F16H 1/28 (20060101); F16D
55/24 (20060101); B60T 1/06 (20060101); F16D
65/00 (20060101); F16D 55/40 (20060101); B60T
1/00 (20060101); F16D 55/00 (20060101); F16H
057/10 (); B60K 017/04 (); B60K 041/26 () |
Field of
Search: |
;74/781R,391,411.5
;180/43B ;192/113B,4A |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Scott; Samuel
Assistant Examiner: Chandlee; Lance W.
Attorney, Agent or Firm: Wegner, Stellman, McCord, Wiles
& Wood
Claims
We claim:
1. In a wheel drive assembly for a vehicle having a rotatably
driven shaft, a sun gear affixed to said shaft, a spindle carried
by the vehicle and encircling a portion of said shaft, a ring gear
fixed on said spindle, a wheel, a hub on said wheel rotatably
mounted relative to said spindle, a planetary carrier fixed to said
hub, a plurality of planet gears carried on said planetary carrier
and engaging between said rotating sun gear and said fixed ring
gear for rotating said wheel relative to said vehicle, a piston
seated in said spindle and having a sleeve encircling said shaft,
said piston and sleeve being axially movable relative to said
spindle, a spring extending between said spindle and said sleeve
for holding said piston retracted in said spindle, brake disc means
carried by said spindle in alignment with said piston, brake disc
means carried by said shaft for rotation with said shaft, said
last-named brake disc means interfitting with said first-named
brake disc means, means for activating said piston to compress said
spring and to lock said first and second-named brake disc means
together whereby the rotation of the second-named brake disc means,
the shaft and the wheel will be stopped.
2. In a wheel drive assembly as claimed in claim 1 wherein said
first-named brake disc means is splined to said non-rotating
spindle for axial movement, and said second-named brake disc means
is splined to said rotating shaft for axial movement.
3. In a wheel drive assembly as claimed in claim 2 wherein a
reaction plate is mounted on said spindle in alignment with said
piston and with said first and second brake disc means.
4. In a wheel drive assembly as claimed in claim 1 wherein said
piston encircles said shaft and is seated in a cavity in said
spindle, and said spring encircles said sleeve and returns the
piston to the retracted position to release the first and second
brake disc means from engagement with each other.
5. In a wheel drive assembly as claimed in claim 1 wherein cooling
fluid encircles a portion of said sun gear, said sun gear and said
planet gears having meshing teeth, a passageway communicates from a
root of the teeth of said sun gear to the first and second brake
disc means, said teeth of the planet gears meshing with the teeth
of the sun gear to force cooling fluid from between the planet
gears and the sun gear through the passageway onto the first and
second brake disc means to cool same.
6. In a wheel drive assembly having a rotatably driven shaft
mounted on a vehicle, a sun gear affixed to said shaft, a spindle
carried by the vehicle and encircling a portion of said shaft, a
ring gear fixed on said spindle, a wheel, a hub on said wheel
rotatably mounted relative to said spindle and having an axially
open end, a planetary carrier removably fixed to said hub around
said open end, a plurality of planet gears carried on said
planetary carrier, said planet gears as carried by said planetary
carrier passing through said open end of said hub and engaging
between said sun gear and said ring gear for rotating said wheel
relative to said vehicle, said planetary carrier and planet gears
being removable from said hub without removing said wheel and hub
from said spindle, a piston encircling said shaft and seated in a
cavity in said spindle, a plurality of non-rotatable brake discs
splined in said spindle and in alignment with each other and in
alignment with said piston, a mating plurality of rotating brake
discs splined on said shaft for rotation with said shaft, with each
rotating disc being interleafed between each pair of said
non-rotating discs, a reaction plate on the opposite end of said
plurality of non-rotating and rotating brake discs, and means for
pressurizing the cavity behind said piston to drive the
non-rotating brake discs into locking relationship with said
rotating brake discs against said reaction plate whereby the
rotation of the shaft and wheel is stopped, said brake discs being
accessible when said planetary carrier and planet gears are removed
from said hub.
7. In a wheel drive assembly for a vehicle having a rotatably
driven shaft, a sun gear affixed to said shaft, a non-rotatable
spindle mounted on the vehicle and encircling a portion of said
shaft, a ring gear fixed on said spindle, a wheel, a hub on said
wheel rotatably mounted relative to said spindle, a planetary
carrier fixed to said hub, a plurality of planet gears carried on
said planetary carrier and engaging between said sun gear and said
ring gear, non-rotatable brake means splined to said spindle,
rotatable brake means splined to said shaft for rotation with said
shaft, and a piston for moving the non-rotating brake means into
locking relationship with said rotating brake means whereby the
rotation of the shaft and wheel will be stopped, said piston
encircles said shaft and is seated in a cavity in said spindle,
spring means acting on said piston to return the piston to a
position to release the first and second brake disc means from
engagement with each other.
8. In a wheel drive assembly as claimed in claim 7 wherein cooling
fluid encircles a portion of said sun gear, said sun gear and said
planet gears having intermeshing teeth, a passageway communicating
from a root of the teeth of said sun gear to the first and second
brake disc means, said teeth on the planet gears meshing with the
teeth on the sun gear to force cooling fluid from between the
planet gears and the sun gear through the passageway onto the first
and second brake disc means to cool same.
9. In a wheel drive assembly as claimed in claim 8 wherein a cap
means is provided on the end of said shaft, said cap means has
collar means encircling the ends of said meshing teeth of the
planet gears and the teeth of said sun gear for providing a close
tolerance so that the meshing teeth of the planet gears and the
teeth of the sun gear will act as a gear pump to pump the cooling
fluid to the brake disc means.
10. In a wheel drive assembly for a vehicle having a rotatably
driven shaft, a sun gear affixed to said shaft, a non-rotatable
spindle mounted on the vehicle and encircling a portion of said
shaft, a ring gear fixed on said spindle, a wheel, a hub on said
wheel rotatably mounted relative to said spindle, said hub having
an axially open end, a planetary carrier removably fixed to the
open end of said hub, a plurality of planet gears carried on said
planetary carrier and engaging between said sun gear and said ring
gear, said planetary carrier and said plurality of planet gears
being removable from said hub without removing said wheel and hub
from said spindle, non-rotatable brake means splined to said
spindle, rotatable brake means splined to said shaft for rotation
with said shaft, and means for moving the non-rotating brake means
into locking relationship with said rotating brake means whereby
the rotation of the shaft and wheel will be stopped, said brake
discs being accessible through the open end of the hub when said
planetary carrier and planet gears are removed from said hub.
11. In a wheel drive assembly as claimed in claim 10 wherein said
non-rotatable brake means are a plurality of brake discs splined
for axial movement relative to said spindle, and said rotatable
brake means are a plurality of brake discs splined for axial
movement relative to said shaft, said rotatable brake discs being
rotated by said shaft and being interleafed between said
non-rotatable brake discs.
12. In a wheel drive assembly as claimed in claim 11 wherein a
non-rotatable reaction plate is carried by said spindle in
alignment with said non-rotatable and rotatable brake discs and in
alignment with said means for moving said brake discs into locking
relationship whereby said last-named means drives said brake discs
against said reaction plate for stopping the rotation of said
shaft.
13. In a wheel drive assembly as claimed in claim 11 wherein said
means for moving the non-rotating brake means into locking
relationship with the rotating brake means is a piston carried by
said spindle in alignment with said non-rotating and said rotating
brake means.
14. In a wheel drive assembly as claimed in claim 10 wherein
cooling fluid encircles a portion of said sun gear, said sun gear
and said planet gears having meshing teeth, a passageway
communicates from a root of the teeth of said sun gear to the first
and second brake disc means, said teeth of the planet gears meshing
with the teeth of the sun gear to force cooling fluid from between
the planet gears and the sun gear through the passageway onto the
first and second brake disc means to cool same.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to land vehicles and, more particularly, to
an improved mounting and servicing arrangement for a brake for a
planetary reduction gear driven wheel for said vehicles.
2. Description of the Prior Art
In land vehicles and, in particular, vehicles such as wheel
loaders, and the like, planetary gear reduction systems have been
mounted on the axle and between the axle and the wheel whereupon
the speed reduction and torque increase of a planetary reduction
gear system is used in advantage for driving the wheel. In some
prior art devices, separate means are mounted on a non-rotatable
axis for driving one element of the planetary gear reduction system
for providing the motive power to the wheel. Such a device is shown
in U.S. Pat. No. 3,812,928 entitled "Electric Powered Wheel" in the
names of Harvey W. Rockwell and William L. Ringland. Various
arrangements have been provided in the prior systems for applying a
braking force to the wheel so as to arrest rotation of the wheel.
In most prior art devices, it is necessary to remove the wheel in
order to gain access to the brake arrangement for providing service
to the brake. Also, in many prior art devices the brakes are
located in such a way that it requires special hydraulic lines to
provide cooling fluid for the brakes, or where the lubricant is
slopping freely within the planetary reduction gear and brake
housing, there has been inadequate cooling of the brakes due to
inadequate amounts of cooling fluid at certain critical points.
These prior devices required hydraulic pumps and conveying means
for directing the hydraulic fluid from the pump to the brake for
cooling purposes.
An additional problem with the prior art devices has to do with the
location of the brakes or the types of brakes used, which required
high torque capacity in order to provide the braking required.
SUMMARY OF THE INVENTION
An improved arrangement for driving a wheel by means of a planetary
reduction gear arrangement between a rotatable axle and the wheel
is provided. The sun gear is driven by the axle with the ring gear
fixed to the housing and the planetary gear carrier being driven by
the sun gear and being connected to the wheel to rotate the wheel.
A disc brake pack is mounted between the rotatable axle and the
fixed housing, which brake pack is activated by hydraulic controls.
The disc brake pack is located in such a way that it is readily
accessible for servicing by simply removing the planetary gear
carrier, with planet gears, from the wheel.
To cool the brake pack, the teeth of the planetary wheels and the
teeth of the sun gear mate in such a way as to pump hydraulic fluid
into the brake pack for cooling the brake pack. In another
embodiment of the invention, the brake pack is located in such a
way that the rotation of the planetary gear carrier serves to
splash cooling fluid on the disc brakes so as to cool the disc
brakes.
The disc brake packs are located between the fixed housing and the
rotatable axle in such a way as to provide lower torque capacity to
affect the braking action between the rotatable wheel and the
housing.
BRIEF DESCRIPTION OF THE DRAWINGS
The details of construction and operation of the invention are more
fully described with reference to the accompanying drawings which
form a part hereof and in which like reference numerals refer to
like parts throughout.
In the drawings:
FIG. 1 is an elevational view of a wheel loader vehicle
incorporating our invention in at least one pair of wheels
thereon;
FIG. 2 is an enlarged, section view through the axle and hub of one
of the wheels of FIG. 1, showing one embodiment of our improved
planetary reduction gear arrangement and brake disc pack; and,
FIG. 3 is another embodiment of our invention with a sectional
view, similar to the sectional view of FIG. 2, only showing the
modified structure of the brake disc pack.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the drawings, FIG 1 illustrates a wheel loader 10 having an
articulated frame 12, the rear portion 14 of which supports an
engine 16 for driving an axle to the rear wheels 18. The front
portion 20 of the frame 12 is pivoted at 22 to the rear portion 14
of the frame and supports the front wheels 24 and a general purpose
bucket 26 on the end of the lift arms 28.
Referring, in particular, to the embodiment shown in FIG. 2, an
axle or shaft 30 is rotatably driven by the engine 16 and projects
outwardly from the housing 32 carried by the frame 12. Although
only one wheel 18 and one end of the shaft 30 is shown and
described, it is to be understood that the same structure is
installed and is operative on the other rear wheel 18 and on the
other end of the shaft 30. In some vehicles, all wheels may be
driven by arrangements that are comparable to the arrangements
described hereinafter. Bolted to the housing 32 is the sleeve or
spindle 34 which is concentrically disposed with respect to the
axle or shaft 30 and has an axially disposed end portion 36 which
has an internal spline 38 formed around the inner surface thereof.
The spindle 34 is secured to the housing 32 by means of bolts or
studs 40 and has seals 41 therebetween. The axle or shaft 30 has a
spline 42 formed in the outer end portion 44 thereof with part of
the spline extending within the confines of the end portion 37 of
the spindle 34.
The outer surface of the outer end portion 36 of the spindle 34 has
an external spline 46 which mates with a spline 48 formed
internally of the cylindrical portion 50 of the ring gear hub 52.
Said ring gear hub 52 has a radially extending flange 52 which has
teeth 54 formed in the outer circumferential surface thereof. The
teeth 54 of the hub engage with the internal spline 56 formed on
the inner surface of the ring gear 58. The ring gear hub 52 is held
in position with respect to the ring gear 58 by means of the split
rings 60 secured on opposite sides of the ring gear hub 52 and
seated in slots in the internal gear teeth 56 of the ring gear 58.
The ring gear 58 and ring gear hub 52 are secured on the outer end
portion 36 of the spindle 34 by means of the positioning ring 62
which is bolted to the hub 52 by bolts 64. The positioning ring 62
has a threaded internal portion 63 which engages the end portion 36
of the spindle 34 through threaded external portion 37.
The rear wheel 18 has a tire 66 mounted on the wheel rim 68 which
has an internal flange 70 bolted by means of bolts 72 to the wheel
hub 74. The wheel hub 74 is rotatably mounted on the spindle 34 by
means of the bearings 76,78. One bearing 76 is seated between the
spindle 34 and the rear portion of the wheel hub 74. The bearing 78
is carried by the cylindrical portion 50 of the ring gear hub 52
and engages the outermost portion of the wheel hub 74. To maintain
a fluid seal between the non-rotatable spindle 34 and the rotatable
wheel hub 74, a duo cone seal 80 is positioned therebetween. In
this way, the rear wheel 18 is rotatable relative to the spindle 34
and housing 32 and the seal 80 maintains lubricant or fluid in a
chamber formed by the wheel hub 74, planetary carrier 104, cap 126
and spindle 34.
Part of the end portion 44 of the axle or shaft 30 extends beyond
the outer end of the end portion 36 of the spindle 34 and has a sun
gear 82 with an internal spline 84 engaging with the spline 42 on
said axle or shaft 30. A snap ring 86 is seated in an opening in
the internal surface of the sun gear 82 so as to secure the sun
gear 82 against axial movement relative to the axle or shaft 30.
The sun gear 82 has external gear teeth 88 and has radial
passageways 90 communicating between the roots of the gear teeth 88
and passageways 92 in the shaft 30. The passageways 92 communicate
into, through and out the end portion of the spline 42 encircled by
the portion 36 of the spindle 34 for a purpose to be described
hereinafter. A reaction plate or ring 94 is bolted by bolts 96 to
the end surface of the spindle 34 and has a bearing washer 98
seated between the one end of the sun gear 82 and the outer face of
said reaction plate or ring 94.
A planetary carrier 104 is bolted by bolts 106 to the axially
facing end of the wheel hub 74. The planetary carrier 104 has three
parallel axially directed pins or pivots 108 secured by split rings
110 in equally spaced apart apertures 112 therethrough. Planet
gears 114 are rotatably mounted on bearings 116 on the pins or
pivots 108 by means of retaining members 118. The teeth 120 on the
planet gears 114 engage with the internal gear teeth 56 in the ring
gear 58. A cap member 122 is positioned around the end of the shaft
30 and has collar portions 124 closely fitting around the ends of
the gear teeth 88 in the sun gear 82 and the teeth 120 on the
planet gears 114. A hub cap or cover 126 is bolted over the cap 122
with the wall of a positioning aperture 128 engaging with the stub
130 of the cap 122. The hub cap 126 is bolted to the outer surface
of the planetary carrier 104 by means of a plurality of bolts
132.
An enlarged cavity or chamber 134 is provided on the inside of the
end portion 36 of the spindle 34. A piston 136 is slidably disposed
in the chamber 134 and has an axially extending reduced diameter
sleeve portion 138 extending through an opening 140 in the spindle
34. A compression spring 142 encircles the reduced diameter sleeve
138 and bears against a shoulder 144 on the spindle 34. A washer
146 is seated between the end of the spring 142 and a snap ring
148, which is nested in a slot in the outer surface of the sleeve
138. The snap ring 148 and washer 146 will retain the spring 142 in
compression against the shoulder 144 on the spindle 34 so as to
urge the piston 136 against the end wall of the chamber 134.
A disc brake pack 150 is positioned between the piston 136 and the
reaction plate or ring 94. The disc brake pack 150 includes
alternate discs or rings 152 which have slots formed in the outer
surface thereof which slots receive the splines 38 in the spindle
34. Between each pair of discs or rings 152 is a disc or ring 154
which has internal slots formed on the inner diameter thereof,
which slots receive the splines 42 formed on the outer surface of
the shaft 30. With the piston 136 positioned against the end wall
of the chamber 134, the discs 152 and 154 will be spaced from each
other so as to permit free rotation of the discs 154 with the shaft
30 relative to the non-rotating discs 152 on the spindle 34. The
splines 38,42 in the slots in the discs 152,154 will permit the
discs to position themselves out of contact with each other when
the piston 136 is in the left-hand position of FIG. 2. When
hydraulic fluid is forced through the tube 156 and bore 158 in the
spindle 34, it will bear against the piston 136 in the chamber 134
to drive the piston 136 to the right and compress the spring 142.
The rotating discs 154 will engage with non-rotating discs 152
thereby stopping rotation of the disc 154 and shaft 30.
With the shaft 30 rotating, the sun gear 82 rotates and drives the
planet gears 114 and planetary carrier 104 relative to the fixed
ring gear 58. The planetary carrier 104 being connected to the
wheel hub 74 will rotate the wheel relative to the housing 32 at a
speed lower than the speed of the shaft 30, but with increased
torque. When it is desired to stop the rotation of the wheel,
hydraulic fluid is forced into chamber 134 for driving the piston
136 to actuate the disc brake pack 150 whereby the rotation of the
shaft 30 will be arrested.
To cool the gears and the brake discs, hydraulic fluid, up to a
certain level, is maintained in the open cavity around the
planetary reduction gear train and brake. To insure that an
adequate amount of cooling fluid flows through the disc brake pack
150, the teeth 120 of the planet gears 114 closely mesh with the
gear teeth 88 of the sun gear 82 to pump hydraulic fluid floating
around the sun gear 82 through the passageways 90 and 92 and into
the open area in which the brake discs 152,154 are located. The
cooling fluid will serve to cool the brake discs 152,154. The
collars 124 on cap 122 will fit close to the end of the sun gear 82
and around the ends of the gear teeth 88 and the teeth 120 so that
the interfit between the teeth 120 and gear teeth 88 will pump the
cooling fluid through passageways 90,92 into the open area around
the disc brake pack 150. A sealing bearing is positioned between
the sleeve 138 of the piston 136 and the outer surface of the shaft
30 to prevent the fluid in the open area surrounding the discs
152,154 from escaping along the shaft 30. Slots 95 are formed in
the inner surface of the reaction plate 94 to permit fluid
communication between the roots of the spline 38 and the chamber
containing the fluid that surrounds the planetary gear train. The
cooling fluid in the open area of the brake pack is forced by
centrifugal force outwardly from the brake discs into the roots of
the spline 38 where it flows through the slots 95 back into the
chamber around the planetary gear train. Rotation of the planetary
carrier 104 and planet gears 114 around the sun gear 82 will serve
to splash or slop the lubricating and cooling fluid around the
moving parts so as to properly lubricate and cool the planetary
reduction gear train.
In the embodiment shown in FIG. 3, may of the parts or elements are
the same as with respect to FIG. 2 and the reference numerals with
respect to said parts or elements in FIG. 2 will be carried over to
the present embodiment. The rotating drive shaft 30 has the spline
42 formed in the outer surface thereon to which, by means of an
internal spline 384, is keyed a flanged sun gear 382. That is,
flanged sun gear 382 has, on one end portion, the sun gear with the
external gear teeth 388 and has an enlarged diametered other end
portion 389 which has splines 391 formed in the outer circumference
thereof. A plurality of brake discs 454 encircle the enlarged
diameter portion 389 of the sun gear 382 and have slots formed in
the inner diameter of the discs 454 which slots are adapted to
receive the splines 391 on the enlarged portion 389 so that the
discs 454 rotate with the sun gear 382 and may move axially with
respect to said sun gear 382.
The spindle 334 has a spline 346 on the external surface of the
outer end portion 336. A ring gear hub 352 has an internal spline
348 engaged with spline 346 in spindle 334 to prevent relative
rotation between the gear hub and spindle. The gear hub 352 has a
radial flange 353 with external teeth 354 engaged with the teeth
356 in the ring gear 358. The ring gear hub 352 is secured to the
spindle 334 against axial movement by means of bolts 361 securing a
retainer 362 in overlapping relation between said spindle 334 and
said hub 352. The ring gear hub 352 is positioned with respect to
the ring gear 358 by means of the snap ring 359 engaging in slots
in the edges of the teeth 356 of the ring gear 358. The wheel hub
374 is rotatably mounted relative to the ring gear hub 352 and the
spindle 334 by means of the bearings 376 and 378, and is sealed by
a seal assembly 380. A ring-type reaction plate 394 has a spline
395 engaging with the teeth 356 in the ring gear 358 and is held in
position relative to the ring gear hub 352 by means of the second
snap ring 360 engaging in slots in the teeth 356 of the ring gear
358. A pressure ring or piston 436 is sealingly positioned in a
chamber 434 formed in the ring gear hub 352 and has a pressurizing
portion 435 between the rear surface of the piston 436 and the wall
of the chamber 434. Passageways 458 communicate through the ring
gear hub 352 and the spindle 334 to the external hydraulic lines
456.
Non-rotating brake discs 452 are interleafed between the rotating
brake discs 454 and have slots formed in the outer circumference
thereof in which slots the teeth 356 of the ring gear 358 slide so
that the brake discs 452 may slide axially with respect to the ring
gear 358 but will be held against rotation with respect to said
ring gear 358. With the drive shaft 30 rotating, the sun gear 382
will rotate the planet gears 114 and planetary carrier 104 against
the fixed ring gear 358 thereby rotating the wheel 18 at a reduced
speed, but at increased torque. The sun gear 382 has splines 391 on
the integrally formed enlarged end portion 389 engaging with and
driving the rotating brake discs 454 in the brake pack 450. To stop
rotation of the wheel 18, fluid under pressure is forced through
the passageways 458 in the spindle 334 and ring gear hub 352 to
drive the piston 436 to the right to lock the non-rotating brake
discs 452 against the rotating brake discs 454 thereby stopping
rotation of the brake discs 454 and of the sun gear 382 and drive
shaft 30. The chamber in which the planetary gears 114 and
planetary carrier 104 rotate has a certain level of hydraulic fluid
maintained therein, which fluid is splashed and agitated by the
rotation of the planetary carrier 104. The splash and agitation of
the fluid will move the fluid past the brake discs 452,454
sufficient to cool the brake discs thereby obviating the need for
pumping additional cooling fluid over the brake discs. A cap 422 is
positioned between the end of the shaft 30 and the inside of the
hub cap 426. The agitation and splash of the fluid in the chamber
by the planetary carrier 104 will also lubricate and cool the
moving parts of the planetary gear train.
For repair, replacement or service to the disc brake pack 150,450
of either the FIG. 2 or FIG. 3 embodiment, it is only necessary to
remove the bolts 106 that retain the planetary carrier 104 against
the wheel hub 74 or 374, which makes it possible to remove the
planetary carrier 104, planet gears 114 and the cap 122,422 from
the sun gear 82,382, ring gear 58,358 and shaft 30. In the FIG. 2
embodiment, the snap ring 86 and sun gear 82 are then removed from
the end of the shaft 30 and the bolts 96 are removed from the
reaction plate 94 so that the reaction plate 94 can be removed to
permit access to the disc brake pack 150. The brake discs 152,154
can then be replaced or serviced without disturbing the mounting of
the wheel 18 on the wheel hub 74. After the disc brake pack 150 has
been serviced, the reverse steps are taken to reassemble the
planetary gear train to the wheel hub 74 and the arrangement is
again ready for operation.
In the FIG. 3 version, after the bolts 106 that retain the
planetary carrier 104 to the wheel hub 374 have been removed, the
planetary carrier 104, planet gears 114 and cap 422 are removed
from the sun gear 382 and ring gear 358. The snap ring 360 is then
removed from the reaction plate 394 whereupon access to the disc
brake pack 450 is obtained. After servicing the disc brake pack
450, reaction plate 394, snap ring 360, and planetary carrier 104
are replaced and bolted to the wheel hub 374 by bolts 106 whereupon
the unit is, once again, ready for use, all without removing the
wheel 18 from the hub 374.
In the FIG. 2 embodiment, a large number of brake discs 152,154 are
employed because the torque due to frictional forces existing at
the interface of the brake discs is proportional to the applied
pressure, to the coefficient of friction between the discs, to the
contact area, and to the means radius of the friction discs.
Because of the small size of the FIG. 2 design discs, a larger
number of discs than those of the FIG. 3 design are required,
assuming that the same pressure and coefficient of friction exist.
In the FIG. 3 version, the brake discs are larger in diameter and
have overall increased braking surface so that fewer brake discs
452,454 are required to affect the same braking torque.
* * * * *